The Model 3D LHe Level Sensor has an outside diameter of 6.35 mm O.D. (1/4″). It is available in active sensing lengths of 1 to 109 cm. Standard overall length is 2 cm longer than the active sensing length (1 cm dead space on either end). For extended inactive lengths select an over all length which includes 1cm dead space at tip, the active length, plus the desired dead space. The sensor is supplied with 4 teflon-insulated hookup leads 30 cm in length. Available are low-loss phosphor-bronze hookup leads.